JP5764639B2 - Mode converter - Google Patents

Description

  The present invention relates to a mode converter, and more particularly to a technique used for a waveguide for communication in the millimeter wave band.

  In recent years, high-speed and large-capacity communication of several G [bps] using the millimeter wave band has been proposed, and a part thereof is being realized. In particular, wireless communication devices operating in the 60 GHz band are becoming more important. In Japan, since a wide frequency band from 59 GHz to 66 GHz can be used without a license, it is expected to spread to the consumer field, and the realization of an inexpensive and small millimeter-wave communication module is urgently needed.

Non-Patent Literature 1 and Non-Patent Literature 2 describe a millimeter wave using a printed circuit board (PWA Post-Wall Waveguide Antenna) as a form for realizing a small and inexpensive millimeter-wave communication module. A module is disclosed.
As shown in FIGS. 1 to 7 of Patent Document 1, in the above technique, the side wall (metal wall) of a conventional waveguide is replaced with a through hole group (post group) of a printed circuit board. A wireless communication IC (CMOS-IC) is mounted on the PWA, and is output from the wireless communication IC (referred to as a semiconductor chip 4 in the specification of Patent Document 1 below) by a method such as wire bonding or bump connection. The transmitted millimeter wave signal is once transmitted through a transmission line (denoted as a line 24 such as a microstrip, a coplanar, or a strip) by a planar circuit, and finally passes through a planar circuit / waveguide conversion structure (denoted as a central conductor 23). To the waveguide structure (denoted as waveguide 2).

Yusuke Kamido, et al., "Through-through-hole mode converter between post-wall waveguide using microstrip line and LCP substrate in 60 GHz band", 2013 IEICE Electronics Society Conference Proceedings, IEICE , September 2013, C-2-70 p. 95. R. Suga, et al. “Cost-FFfective 60-GHz Antenna-Package with End-Fire Radiation from Open-Ended Post-Wall Waveguid FF or Wireless File-Transfer System,” 2011 IEEE MTT-S International Microwave Symposiμm, pp. 348-351

In the mode converter shown in Non-Patent Document 1, since the excitation via is a through hole, the metal column of the excitation via is exposed on the second main surface side of the substrate.
For this reason, in actual use, the metal pillar of the excitation via is affected by other metal bodies such as a casing, the input impedance viewed from the end face of the excitation via varies, and the magnitude of the reflection loss varies. There was a problem.

  This invention is made | formed in view of the situation mentioned above, Comprising: It aims at providing the mode converter which can suppress the fluctuation | variation of the reflection loss by a metal body adjoining.

As shown in FIG. 22, the present inventor measured the reflection loss (vertical axis) with respect to the frequency (horizontal axis) when three types of members were brought close to the bottom of the conventional mode converter. In this experiment, the reflection loss (a) measured by bringing quartz into contact with the bottom of the mode converter to avoid the influence of the proximity of the metal to the bottom of the mode converter, and the reflection loss (b) measured by bringing the metal plate close to the bottom of the mode converter. And a reflection loss (c) measured by sandwiching a paper having a thickness of 85 μm between the bottom surface of the mode converter and the metal plate.
As a result, it was found that there is a clear difference in the magnitude of reflection loss between the state where the metal is not close (a) and the state where the metal is close (b).
On the other hand, when paper was sandwiched (c), the reflection loss was found to be almost equal to (a) without the influence of metal. Based on this finding, the present invention is configured as follows to reduce the influence of metal.

The present invention is a mode converter for mutually converting a signal between a transmission line and a waveguide, the first substrate having a first main surface and a second main surface opposite to the first main surface, and the first substrate A second substrate laminated on the first main surface side of the substrate; a planar circuit including the transmission path; formed on the second substrate for propagating a high-frequency signal; and connected to the planar circuit; A conductive excitation pin penetrating through the substrate and the second substrate; a ground conductor layer formed on each of the main surfaces of the first substrate; and the waveguide having a conductive wall portion connecting them to each other. The excitation pin includes a conductive penetrating portion penetrating the first substrate and the second substrate, a conductive first portion projecting from the penetrating portion in the diameter increasing direction on the first main surface side, and the first pin Conductive second projecting in the diameter increasing direction from the penetrating portion on the two principal surface sides Minutes, has, between the first portion of the excitation pins and the ground conductor layer of the first main surface side, and, with the second portion of the excitation pin and the second main surface side of the ground conductor layer There is provided a mode converter in which antipads are respectively formed and an insulating resin layer covering at least the end portions of the excitation pins and the antipads is provided on the ground conductor layer on the second main surface side.
The transmission line constitutes a microstrip line, one end side is connected to the excitation pin, the other end side is connected to a pad, and a GND pad is separated from the pad on both sides of the pad. The formed GND pad may be connected to the ground conductor layer through a GND connection via.
The insulating resin layer may be composed of a thermosetting resin.
The insulating resin layer may be composed of a liquid crystal polymer.
The insulating resin layer may include a liquid crystal polymer layer made of a liquid crystal polymer, and a thermosetting resin layer interposed between the liquid crystal polymer layer and the ground conductor layer on the second main surface.
Preferably, the wall portion is a post wall formed of a plurality of conductive posts respectively formed in a plurality of through holes penetrating between both main surfaces of the first substrate.

  According to the present invention, since the insulating resin layer for suppressing the influence of the adjacent metal is provided on the ground conductor layer laminated on the second main surface of the first substrate, the input impedance of the metal proximity viewed from the end surface of the excitation pin is It is possible to prevent fluctuations from the design value and suppress fluctuations in reflection loss.

(A) It is a perspective view which shows typically the structure of the mode converter which concerns on 1st embodiment of this invention. (B) It is a schematic block diagram which shows the side surface of the mode converter shown to (A). It is a top view of the mode converter of FIG. It is sectional drawing which shows schematic structure of the mode converter which concerns on 1st embodiment. It is sectional drawing which shows the 1st process in the manufacturing process of a mode converter. It is sectional drawing which shows the 2nd process in the manufacturing process of a mode converter. It is sectional drawing which shows the 3rd process in the manufacturing process of a mode converter. It is sectional drawing which shows the pre-process of the 4th process in the manufacturing process of a mode converter. It is sectional drawing which shows the 4th process in the manufacturing process of a mode converter. It is sectional drawing which shows the pre-process of the 5th process in the manufacturing process of a mode converter. It is sectional drawing which shows the 5th process in the manufacturing process of a mode converter. It is sectional drawing which shows the 6th process in the manufacturing process of a mode converter. It is sectional drawing which shows the 7th process in the manufacturing process of a mode converter. It is sectional drawing which shows the pre-process of the 8th process in the manufacturing process of a mode converter. It is sectional drawing which shows the 8th process in the manufacturing process of a mode converter. It is sectional drawing which shows the pre-process of the 9th process in the manufacturing process of the mode converter which concerns on 1st embodiment. It is sectional drawing which shows the 9th process in the manufacturing process of the mode converter which concerns on 1st embodiment. It is sectional drawing which shows the pre-process of the 9th process in the manufacturing process of the mode converter which concerns on 2nd embodiment. It is sectional drawing which shows the 9th process in the manufacturing process of the mode converter which concerns on 2nd embodiment. It is sectional drawing which shows the pre-process of the 9th process in the manufacturing process of the mode converter which concerns on 3rd embodiment. It is sectional drawing which shows the 9th process in the manufacturing process of the mode converter which concerns on 3rd embodiment. It is a figure explaining electric field distribution generated by the mode converter concerning the present invention. In a mode converter, it is a graph which shows the relationship of the reflection coefficient (vertical axis) with respect to a frequency (horizontal axis).

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.
The following embodiments are described by way of example in order to better understand the gist of the invention, and do not limit the present invention unless otherwise specified. In addition, in the drawings used for the following description, in order to make the features of the present invention easier to understand, the main part may be enlarged for the sake of convenience, and the dimensional ratios of the respective components are the same as the actual ones. Not necessarily.

  The structure of the mode converter 1 which concerns on one Embodiment of this invention is demonstrated using FIGS. 1-3. FIG. 1A and FIG. 1B are diagrams schematically showing the configuration of the mode converter 1. FIG. 2 is a plan view of the mode converter 1. FIG. 3 is a sectional view of the mode converter 1.

  As shown in FIGS. 1 to 3, the mode converter 1 penetrates the first substrate 10, the second substrate 42, the planar circuit C including the signal transmission path C <b> 1 for high-frequency signal propagation, and the substrates 10 and 42. And the waveguide 40 (see FIG. 3).

The 1st board | substrate 10 can be set as the structure by which copper foil 3a, 3b was laminated | stacked on both surfaces of the base material 2 (refer FIG. 3).
The substrate 2 is made of, for example, a single layer LCP (liquid crystal polymer). Since LCP is a thermoplastic resin, it is possible to fabricate CCL by bonding desired copper foils 3a and 3b on both sides of LCP and thermally fusing them by hot pressing. LCP is a material suitable for high-frequency transmission because it has a low dielectric constant and relative dielectric constant and hardly absorbs water, and can exhibit sufficient characteristics even in the millimeter wave band.

  As shown in FIG. 3, the first substrate 10 has a main surface 10 a (first main surface) and a main surface 10 b (second main surface) which is the opposite surface. In the first substrate 10, through holes 11 to 13 (first through hole 11, second through hole 12, and third through hole 13) penetrating between the main surfaces 10 a and 10 b are formed.

As shown in FIG. 3, the excitation pin 22 has a metal layer 22 a (conductor layer) provided on the inner wall 12 a of the second through hole 12. The metal layer 22a reaches the signal transmission path C1.
The conductor column 21 has metal layers 21 a and 21 b (conductor layer) provided on the inner wall 11 a of the first through hole 11. The metal layer 21 a reaches the conductor film 14 and the conductor film 15 formed on the main surfaces 10 a and 10 b of the first substrate 10.
The GND connection via 23 has a metal layer 23 a (conductor layer) provided on the inner wall 13 a of the third through hole 13. The metal layer 23a reaches the signal transmission path C1.
Hereinafter, the conductor pillar 21, the excitation pin 22, and the GND connection via 23 may be collectively referred to as a pin 20.

The planar circuit C is laminated on the ground conductor layer 30 on the main surface 10a of the first substrate 10 via the adhesive layer 16 and the dielectric layer 17 via the copper foil 18. Signal transmission path C1.
In the planar circuit C, when a high frequency signal (millimeter wave signal) is applied to the end of the signal transmission path C1, a TEM mode electromagnetic wave propagates between the signal transmission path C1 and the ground conductor layer 30.

  The dielectric layer 17 that forms the planar circuit C and the copper foil 18 laminated on the dielectric layer 17 constitute a second substrate 42. As the dielectric layer 17, a film made of LCP (liquid crystal polymer) can be used.

The conductor film 14 is formed on the main surface 10a of the first substrate 10, and constitutes the ground conductor layer 30 together with the copper foil 3a on the main surface 10a. The conductor film 15 is formed on the main surface 10b of the first substrate 10 and constitutes the ground conductor layer 31 together with the copper foil 3b.
Each of the ground conductor layers 30 and 31 is made of a conductor such as copper and functions as an electrically grounded wiring (GND).
In addition, since the copper foil 3a can be handled as a part of the ground conductor layer 30, the upper surface of the base material 2 can also be regarded as the main surface 10a. Similarly, since the copper foil 3b can be handled as a part of the ground conductor layer 31, the lower surface of the substrate 2 can be regarded as the main surface 10b.

The waveguide 40 includes ground conductor layers 30 and 31 disposed on one main surface 10a and the other main surface 10b of the first substrate 10 and a post wall 21A. The post wall 21 </ b> A is composed of a plurality of conductor columns (posts) 21 erected between the ground conductor layers 30 and 31 and connecting the two.
As shown in FIG. 1A, the plurality of conductor pillars 21 constituting the post wall 21A are arranged so as to surround the excitation pin 22 in a U shape in a plan view of the first substrate 10.

  The distance between the central axes of the conductor columns 21 is preferably set to be the same as or smaller than twice the diameter of the conductor columns 21. As a result, the distance between the adjacent conductor columns 21 is equal to or less than the diameter of the conductor columns 21, and the effect of preventing leakage by reflecting electromagnetic waves excited from the excitation pins 22 can be enhanced.

  In the illustrated example, a post wall 21A composed of a plurality of conductor pillars 21 is employed, but instead, a continuous wall composed of a conductor plate such as a metal plate extending so as to surround the excitation pin in a U shape. A simple wall may be employed.

On the main surface 10 a of the first substrate 10, an antipad 32 is formed around the excitation pin 22. An antipad 33 is formed around the end 22b of the excitation pin 22 on the main surface 10b.
The antipads 32 and 33 are formed around the excitation pin 22 in an annular shape, and by securing a region for insulating the ground conductor layers 30 and 31 and the excitation pin 22, the input impedances of the planar circuit C and the excitation pin 22 are reduced. Impedance matching.

The antipads 32 and 33 are insulating regions extending outward from the opening of the second through hole 12, and may be, for example, annular regions around the excitation pin 22 where the ground conductor layers 30 and 31 are not formed.
The anti-pads 32 and 33 may be an electrically insulating region, and may be constituted by a gap secured between the excitation pin 22 and the ground conductor layers 30 and 31, or an insulation filled in the gap. You may comprise by a body (resin etc.).
In the illustrated example, the antipad 33 on the main surface 10b side is filled with a resin constituting the insulating resin layer 41.

One end of the signal transmission path C1 is connected to the outer end of the excitation pin 22, and the other end is connected to the GSG pad 34, thereby forming a microstrip line.
As shown in FIG. 2, GND pads 35 are formed on both outer sides of the GSG pad 34 so as to be separated from the GSG pad 34. The GND connection via 23 is connected to the GND pad 35. The GND connection via 23 is formed to reach the ground conductor film 31.
The conductor pillar 21, the excitation pin 22, and the GND connection via 23 described above only have to be formed at least on the surface from a conductor such as Cu, Ag, Au, and the inside is the same conductor, cavity, or A structure occupied by an insulating resin or the like can be employed.
As shown in FIG. 3, in this example, the resin constituting the insulating resin layer 41 provided on the other main surface 10 b side of the first substrate 10 is filled in the conductor pillars 21, the excitation pins 22, and the GND connection vias 23. ing.

An insulating resin layer 41 is formed on the lower surface side of the ground conductor layer 31 on the main surface 10b side. The specific configuration of the insulating resin layer 41 will be described in detail in a ninth step (see FIGS. 15 to 20) described later.
The insulating resin layer 41 in the illustrated example is formed in the entire region on the lower surface side of the ground conductor layer 31, but the insulating resin layer 41 is not necessarily formed in the entire region on the lower surface side of the ground conductor layer 31, and at least The end 22b of the excitation pin 22 (the end on the second main surface 10b side) and the antipad 33 may be covered. For example, in the region on the lower surface side of the ground conductor layer 31, it may be formed only in a partial region including the end 22 b of the excitation pin 22 and the antipad 33.
“Covering at least the end 22b of the excitation pin 22 and the antipad 33” means having a region overlapping the end 22b of the excitation pin 22 and the antipad 33 in plan view.

In the mode converter 1, when a high frequency signal is input to the signal transmission path C1 in the planar circuit C, an electric field is generated between the signal transmission path C1 and the waveguide upper wide wall 14, and an electromagnetic wave propagates as a microstrip mode.
The electromagnetic wave induces a TE mode in the waveguide substrate 10 using the excitation pin 22 as a new TE mode excitation source, and propagates in the waveguide substrate 10 as the TE mode.

An example of a method for manufacturing the mode converter 1 shown in FIGS. 1 to 3 will be described step by step with reference to FIGS.
First, as a first step, as shown in FIG. 4, a so-called copper clad laminate (CCL) in which a copper foil 103a and a copper foil 103b are bonded to both surfaces of an LCP film 102 as a base material. A first substrate 110 made of is prepared. The first substrate 110 corresponds to the first substrate 10 shown in FIGS.

Since LCP (liquid crystal polymer) is a thermoplastic resin, it is possible to produce CCL by bonding desired copper foils 103a and 103b on both sides of the LCP and heat-sealing by hot pressing. The thickness of the copper foils 103a and 103b bonded to both sides is preferably 12 μm or more in consideration of the handling property at the time of bonding with the LCP. However, after CCL preparation by hot press, a chemical solution such as sulfuric acid / hydrogen peroxide is used. It is possible to adjust to a desired thickness by dissolving and removing some of the copper foils 103a and 103b.
In addition, since the thickness of copper foil 103a, 103b affects subsequent circuit formation property, the thinner one is preferable in the range which does not have influence when flowing an electric signal. Moreover, the thickness of the LCP film 102 is, for example, 100 μm to 750 μm. The thickness of the copper foils 103a and 103b is, for example, 2 to 18 μm.

Next, as shown in FIG. 5, as a second step, the first through hole 111 reaching from the one main surface 110 a of the first substrate 110 to the other main surface 110 b is formed by drilling.
The hole diameter of the first through hole 111 can be adjusted according to the diameter of the drill blade to be used, and can be appropriately set in the range of, for example, 75 μm to 500 μm according to the application of the component to be manufactured.
The first through hole 111 corresponds to the first through hole 11 in FIGS.

Next, a conductive film is formed on the wall surface of the first through-hole 111 as a base formation step that is a pre-step of the second step. The conductive film is formed using a known method such as DPP (Direct Plating Process).
This conductive film can be composed of palladium, carbon, or the like, but it is sufficient that copper plating is possible by electrolytic copper plating in the third step described later. There is no particular limitation.

Next, copper plating is performed as a third step. As shown in FIG. 6, a copper plating layer is formed on one main surface 110 a of the first substrate 110, the other main surface 110 b, and the inner wall surface of the first through hole 111. Form. The plating layer formed on one main surface 110 a of the first substrate 110 is a plating layer 114, and the plating layer formed on the other main surface 110 b is a plating layer 115, and is formed inside the first through hole 110. The plating layer is a conductor column 121.
A conductor layer made of the copper foil 103a and the plating layer 114 is called a ground conductor layer 130, and a conductor layer made of the copper foil 103b and the plating layer 115 is called a ground conductor layer 131.
Considering that the thickness of the plating layer is preferably thicker than the skin depth by the millimeter wave band signal, the skin depth at the signal of 60 GHz is 270 nm. 2 μm or more is considered sufficient.
The conductor pillar 121, the ground conductor layer 130, and the ground conductor layer 131 correspond to the conductor pillar 21, the ground conductor layer 30, and the ground conductor layer 31 in FIGS.

As a pre-process of the fourth process, as shown in FIG. 7, an anti-pad forming etching resist 150 is formed on the ground conductor layer 130 of the first substrate 110, and an etching resist 151 is formed on the ground conductor layer 131. .
As a method of forming the etching resists 150 and 151, a known method can be used. For example, the following method can be used. First, a photosensitive dry film is laminated on the ground conductor layer 130 and the ground conductor layer 131 of the first substrate by a hot roll. Next, the dry film is patterned into a desired shape by using a photolithography method to obtain an etching resist.
In this structure, since the circuit formation such as an antipad is not performed on the ground conductor layer 131 in the fourth step, the etching resist 151 is formed on the entire surface of the ground conductor layer 131. That is, the etching resist 151 formed on the ground conductor layer 131 is used only to protect the ground conductor layer 131 from the copper etchant.

As a fourth step, as shown in FIG. 8, an antipad 132 is formed on the ground conductor layer 130 by wet etching, which is a known method, using the etching resist formed earlier as a mask. A chemical solution such as ferric chloride or cupric chloride can be used as the etching solution. However, these etchants are merely examples and are not limited to these.
After the etching, the etching resist is peeled off. As the stripping solution, a sodium hydroxide aqueous solution or a potassium hydroxide aqueous solution is generally used. The stripping solution is preferably a recommended chemical solution depending on the etching resist to be used.

Next, as a pre-process of the fifth process, as shown in FIG. 9, a second substrate 142 made of a so-called copper-clad laminate in which a copper foil 118 is bonded to one side of an LCP film 117 is prepared. The thickness of the LCP film 117 is, for example, 12 to 100 μm, and the thickness of the copper foil 118 bonded to one surface thereof is, for example, 2 to 18 μm.
The second substrate 142 corresponds to the second substrate 42 in FIGS.

  As a fifth step, as shown in FIG. 10, the second substrate 142 is laminated on the ground conductor layer 130 via the adhesive sheet 116. At this time, the lamination is performed such that one surface of the LCP film 117 of the second substrate 142 faces the adhesive sheet 116. As a result, the laminated substrate 200 having a structure in which the first substrate 110 and the second substrate 142 are laminated via the adhesive sheet 116 is obtained.

An example of the lamination method in the fifth step is given. First, the adhesive sheet 116 is thermally laminated at 50 to 100 ° C. on the ground conductor layer 130, and then the second substrate 142 is thermally laminated at 50 to 100 ° C. on the adhesive sheet 116. Then, it is possible to heat-cure and laminate | stack an adhesive bond layer, applying a pressure using a pressurization hot press machine. The pressure is generally 25 to 65 kgf / cm ² and the temperature is generally about 140 to 200 ° C.

As a sixth step, as shown in FIG. 11, a predetermined position of the laminated substrate 200 obtained earlier is reached by drilling from one main surface 200a of the laminated substrate 200 to the other main surface 200b. Two through holes 112 and a third through hole 113 are formed.
The second through hole 112 is formed inside the antipad 132 formed in the ground conductor layer 130.
In this embodiment, the hole diameter of the 2nd through-hole 112 and the 3rd through-hole 113 can be adjusted with the diameter of the drill blade to be used, and it sets suitably in the range of 75 micrometers-500 micrometers, for example according to the use of the components to manufacture. can do.
The second through hole 112 and the third through hole 113 correspond to the second through hole 12 and the third through hole 13 in FIGS.

In the sixth step, it is necessary to align the laminated substrate 200 and the drilling device so that holes (second through hole 112 and third through hole 113) are formed at predetermined positions when drilling. There is. A known method can be used as the alignment method.
As an example, alignment marks are formed on the ground conductor layer 130 simultaneously with the formation of the antipad 132 on the ground conductor layer 130. After the lamination in the fifth step, the X-ray image processing apparatus recognizes the guide mark formed on the ground conductor layer 130, and opens the pin hole for inserting the pin toward the guide mark. Further, a pin longer than the thickness of the laminated substrate 200 is inserted into the pin hole. Furthermore, it is possible to adopt a method of aligning the substrate and the drilling device by inserting the inserted pin into a reference hole on the processing stage of the drilling device.

  Next, a conductive film is formed on the wall surfaces of the second through-hole 112 and the third through-hole 113 as a base formation step that is a pre-step of the seventh step. For details, it is possible to use the same technique as that described in the third step.

Next, as a seventh step, copper plating is performed, and as shown in FIG. 12, one main surface 200a, the other main surface 200b, the inner wall surface of the second through-hole 112, and the third through-hole of the laminated plate 200 A copper plating layer is grown on the inner wall surface of the hole 113.
Here, the plating layer on the main surface 200a side is the plating layer 201a, the plating layer on the main surface 200b side is the plating layer 201b, the plating layer formed inside the second through hole 112 is the excitation pin 122, and the third The plating layers formed inside the through holes 113 are denoted as GND connection vias 123, respectively.
Further, the copper foil and the plating layer on one main surface 200a side of the multilayer substrate 200 are collectively referred to as a ground conductor layer 202, and the copper foil and the plating layer on the other main surface 200b side are collectively referred to as a ground conductor layer 203. write.
The excitation pin 122 and the GND connection via 123 correspond to the excitation pin 22 and the GND connection via 23 of FIGS.

As a pre-process of the eighth process, as shown in FIG. 13, an etching resist 152 for forming an anti-pad, microstrip line, and GND pad is formed on the ground conductor layer 202 of the multilayer substrate 200, and the ground conductor layer 203 is formed. Then, an etching resist 153 for forming an antipad is formed.
As a method for forming the etching resist, the known methods mentioned in the fourth step can be used.

Next, as an eighth step, as shown in FIG. 14, a microstrip line 128 (FIG. 1) connected to the excitation pin 122 on the ground conductor layer 202 by an etching method using the etching resist 152 formed in the previous step as a mask. (Corresponding to the signal transmission path C1 in FIG. 3) and the GND pad 135 are formed to form the planar circuit C. Further, an antipad 133 is formed on the ground conductor layer 203.
As an etching method, it is possible to use wet etching which is a known method as mentioned in the fourth step.

Next, as a pre-process of the ninth step, as shown in FIG. 15, a thermosetting resin layer 141A (insulating resin layer 141) to be laminated on the ground conductor layer 203 is prepared.
In FIG. 16, as the ninth step, a thermosetting resin layer 141A is laminated on the ground conductor layer 203 of the first substrate 110, and a single insulating resin layer 141 is formed by hot pressing.
Thereby, the mode converter 1 shown in FIGS. 1-3 is obtained.

The thermosetting resin layer 141A is required to have a low dielectric constant and a low dielectric loss tangent. A commercially available general-purpose product can be used as the thermosetting resin. As the thermosetting resin, it is possible to use an epoxy resin or a polyphenylene ether (PPE) resin. The volume resistivity of the epoxy resin is 10 ¹² to 10 ¹⁷ Ω · cm. The volume resistivity of PPE is about 10 ¹⁷ Ω · cm.

The thickness of the thermosetting resin layer 141A is, for example, 50 μm to 200 μm (preferably 50 μm to 100 μm). The conditions of the hot press depend on the characteristics of the adhesive layer, but a treatment at a temperature of 160 ° C., a pressure of 45 kfg / cm ² , and a time of about 60 minutes is common. This construction method has an advantage that the processing temperature is low and the productivity is high as compared with the case where the LCP film described in the third embodiment (described later) is directly heat-sealed.
At the time of hot pressing, resin is embedded in the excitation pin 122 or in the GND connection via, but in either case, the characteristics to the mode converter are not affected, and there is no problem.
The insulating resin layer 141 corresponds to the insulating resin layer 41 in FIGS.

In the mode converter 1, an insulating resin layer 41 (141) made of a thermosetting resin is provided on the ground conductor layer 31 (131) formed on the second main surface 10a (110a) of the first substrate 10 (110). It was.
By the insulating resin layer 41 (141), it is possible to prevent fluctuations in the input impedance viewed from the end face of the excitation pin 21 (121) and to suppress fluctuations in the reflection loss.

The insulating resin layer 141 in the illustrated example is formed in the entire region on the lower surface side of the ground conductor layer 203, but the insulating resin layer 141 is not necessarily formed in the entire region on the lower surface side of the ground conductor layer 203, and at least The end 122b (end on the second main surface 10b side) of the excitation pin 122 and the antipad 133 may be covered. For example, in the region on the lower surface side of the ground conductor layer 203, it may be formed only in a partial region including the end 122 b of the excitation pin 122 and the antipad 133.
“Covering at least the end portion 122b of the excitation pin 122 and the antipad 133” means having a region overlapping the end portion 122b of the excitation pin 122 and the antipad 133 in plan view.

(Second embodiment)
A second embodiment of the present invention will be described with reference to FIGS. 17 and 18.
The mode converter 1A of the second embodiment is different from the first embodiment in the specific configuration of the insulating resin layer 141 shown in the ninth step (see FIGS. 15 and 16).

In the previous step of the ninth step in the second embodiment, as shown in FIG. 17, as the insulating resin layer 141, a thermosetting resin layer 141B that becomes an adhesive layer, and an LCP film 141C that consists of LCP (liquid crystal polymer) Prepare.
As shown in FIG. 18, as the main step of the ninth step, a thermosetting resin layer 141B is thermally laminated on the ground conductor layer 203, and an LCP film 141C, which is an insulating resin layer, is further formed on the thermosetting resin layer 141B. Heat laminate. Thereafter, hot pressing is performed to form an insulating resin layer 141 in which the thermosetting resin layer 141B and the LCP film 141C (liquid crystal polymer layer) are integrated.
The thermosetting resin layer 141B is interposed between the LCP film 141C and the ground conductor layer 203.

The thermosetting resin layer 141B is required to have a low dielectric constant and a low dielectric loss tangent, but a commercially available general-purpose product can be used.
Moreover, as a layer on the thermosetting resin layer 141B, polyimide, Teflon (registered trademark), a glass epoxy plate, or the like can be used in addition to the LCP film 141C.
The thermosetting resin layer 141B can have a thickness of 12 to 50 μm, and the LCP film 141C can have a thickness of 25 to 500 μm.

The conditions of the hot press depend on the characteristics of the thermosetting resin, but a treatment at a temperature of about 160 ° C., a pressure of 45 kfg / cm ² , and a time of about 60 minutes is common. This construction method has an advantage that the processing temperature is low and the productivity is high as compared with the case where the LCP film described in the third embodiment is directly heat-sealed.

According to the mode converter 1A of the second embodiment, the thermosetting property that becomes an adhesive layer on the ground conductor layer 31 (131) laminated on the second main surface 10a (110a) of the first substrate 10 (110). An insulating resin layer 41 (141) made of a laminate of the resin layer 141B and the LCP film 141C was provided.
The insulating resin layer 41 (141) can prevent fluctuations in the input impedance viewed from the end face of the excitation pin 21 (121) and suppress fluctuations in reflection loss.

  When compared with the first embodiment, the mode converter 1A of the second embodiment can arbitrarily change the thickness of the insulating layer by changing the thickness of the insulating resin layer (141C) to be bonded to the thermosetting resin layer 141B. There is a merit that can be set. That is, the thermosetting resin layer 141B needs to be cured by heat and cannot be made too thick. However, the thickness of the insulating resin layer 141 can be reduced by selecting the thickness of the second LCP film 141C. Can be set arbitrarily.

(Third embodiment)
A third embodiment of the present invention will be described with reference to FIGS. 19 and 20.
The mode converter 1B shown in the third embodiment is different from the first and second embodiments in the specific configuration of the insulating resin layer 141 shown in the ninth step (see FIGS. 15 to 18).

In the previous step of the ninth step in the third embodiment, as shown in FIG. 19, an LCP film 141D (liquid crystal polymer layer) made of LCP (liquid crystal polymer) is used alone as the insulating resin layer 141.
As shown in FIG. 20, as the ninth step, an LCP film 141D is laminated on the ground conductor layer 203, and a single insulating resin layer 141 is formed by hot pressing.

Since the LCP constituting the LCP film 141D is a thermoplastic resin, as shown in FIG. 20, the LCP film can be directly laminated on the substrate by hot pressing at a temperature near the melting point.
Specifically, after the LCP film 141D is overlaid on the ground conductor layer 203, heat treatment is used to heat and insulate by processing at a temperature of 300 ° C., a pressure of 45 kfg / cm ² , and a time of about 10 minutes. A resin layer 141 is formed. The thickness of the LCP film is, for example, 25 μm to 500 μm.
In the third embodiment, unlike the first and second embodiments, since the insulating resin layer 141 is an LCP single layer, it is possible to form an insulating layer having a low dielectric constant and a low dielectric loss tangent. The effect of suppressing reflection loss can be expected.

Next, an experimental example using the above-described mode converter will be described.
In the case of using the mode converter according to the present embodiment, the end of the microstrip line is used as a port, and a simulation about reflection loss is performed. Three-dimensional electromagnetic field analysis software HFSS was used for the simulation. The results are shown in FIG.
In the mode converter of the present embodiment, the excitation pin has a diameter of 200 μm, the diameter of the land portion of the excitation pin is 350 μm, and the space width (excitation of the antipad (32, 33) positioned around the excitation pin) The width along the radial direction of the pins was set to 85 μm, 100 μm, 125 μm, 135 μm, and 150 μm. Further, the horizontal axis of the graph indicates the frequency, and the vertical axis indicates the magnitude of the reflection loss.
From this figure, it was found that the magnitude of the reflection loss varies depending on the size of the antipad. Therefore, from this result, it was found that the input impedance at the pin input end can be controlled by adjusting the size of the antipad.
Further, it is preferable to select an antipad size of 100 μm to 150 μm and an optimum value of 125 μm, and it has been found that the reflection loss can be significantly reduced by selecting the optimum value.

  As mentioned above, although embodiment of this invention was explained in full detail with reference to drawings, the concrete structure is not restricted to this embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included. For example, the antipad may be formed only on one of the first main surface and the second main surface of the first substrate.

  The present invention relates to a mode converter, and more particularly to a technique used for a waveguide for communication in the millimeter wave band.

  10, 100 ... first substrate, 10a, 100a ... main surface (first main surface), 10b, 100b ... main surface (second main surface), 11, 111 ... first through hole , 12, 112 ... second through hole, 13, 113 ... third through hole, 17, 117 ... dielectric layer, 22, 122 ... excitation pin, 22b, 122b ... excitation pin , GND connection vias, 30, 130... Ground conductor layer, 31, 131... Ground conductor layer, 40... Waveguide, 32, 132, 33, 133. Antipad, 41, 141 ... insulating resin layer, 42, 142 ... second substrate, 141A ... thermosetting resin layer, 141B ... thermosetting resin layer, 141C ... LCP film (Liquid crystal polymer layer), 141D ... LCP film (liquid crystal polymer layer), C · Planar circuit, C1 · · · signal transmission path.

Claims (6)

A mode converter for mutually converting signals between a transmission line and a waveguide,
A first substrate having a first main surface and a second main surface opposite to the first main surface;
A second substrate laminated on the first main surface side of the first substrate;
A planar circuit that includes the transmission path and is formed on the second substrate to propagate a high-frequency signal;
A conductive excitation pin connected to the planar circuit and penetrating the first substrate and the second substrate;
A ground conductor layer formed on each main surface of the first substrate and the waveguide having a conductive wall portion connecting them to each other;
The excitation pin includes a conductive penetrating portion penetrating the first substrate and the second substrate, a conductive first portion protruding from the penetrating portion in the diameter increasing direction on the first main surface side, and the second A conductive second portion protruding in the diameter increasing direction from the penetrating portion on the main surface side,
Antipads are provided between the ground conductor layer on the first main surface side and the first portion of the excitation pin, and between the ground conductor layer on the second main surface side and the second portion of the excitation pin, respectively. Formed,
The mode converter, wherein the grounding conductor layer on the second main surface side is provided with an insulating resin layer covering at least the end portion of the excitation pin and the antipad. The transmission path constitutes a microstrip line, one end side is connected to the excitation pin, and the other end side is connected to a pad formed on the second substrate,
On both sides of the pad, GND pads are formed separately from the pad,
The mode converter according to claim 1, wherein the GND pad is connected to the ground conductor layer through a GND connection via.   The mode converter according to claim 1, wherein the insulating resin layer is made of a thermosetting resin.   The mode converter according to claim 1, wherein the insulating resin layer is made of a liquid crystal polymer.   The said insulating resin layer consists of a liquid crystal polymer layer which consists of a liquid crystal polymer, and a thermosetting resin layer interposed between the said liquid crystal polymer layer and the grounding conductor layer of said 2nd main surface. Mode converter.   The said wall part is a post wall which consists of a some electroconductive post each formed in the inside of the some through-hole penetrated between both the main surfaces of said 1st board | substrate, The any one of Claims 1-5 The mode converter described in the paragraph.

Images